1. Field of the Invention
The present invention relates to an apparatus and method for controlling an operation of a reciprocating compressor and, more particularly, to an apparatus and method for controlling an operation of a reciprocating compressor capable of independently controlling top and bottom dead centers.
2. Description of the Related Art
In general, a reciprocating compressor can vary compression capacity by changing a compression ratio of a reciprocating compressor by controlling a voltage applied to a motor within the compressor.
The reciprocating compressor will be described in detail with reference to FIG. 1
FIG. 1 is a schematic block diagram showing an apparatus for controlling operations of a reciprocating compressor according to a related art.
As shown in FIG. 1, the related art apparatus for controlling an operation of a reciprocating compressor includes a reciprocating compressor having certain compression capacity as a piston positioned therein moves in a vertical direction by a voltage that controls a stroke according to a stroke command value (stroke reference value); a voltage detection unit 12 for detecting a voltage applied to the reciprocating compressor; a current detection unit 11 for detecting current flowing at the reciprocating compressor; a microcomputer 13 for calculating the stroke estimate value based on the detected voltage and current, and outputting a switching control signal based on the comparison result of the calculated stroke estimate value and the stroke command value; and a triac (Tr1) switched on or off according to the switching control signal to thus control a flow of current of general AC input power source.
The apparatus for controlling an operation of the reciprocating compressor controls a motor of the reciprocating compressor by turning on or off general AC input power (AC 220V) by controlling an ON/OFF operation of the triac Tr1.
Herein, because the general AC input power is an AC voltage, voltage (positive (+) voltage) of one half period of the general AC input power is used to control a position of a top dead center (TDC) of the piston and voltage (negative (−) voltage) of the other half period of the general AC input power is used to control a position of a bottom dead center (BDC) of the piston.
The TDC refers to a position of an upper surface of the piston when the reciprocating compressor performs a suction stroke (namely, when the piston is lifted up to its maximum level. The BDC refers to a position of the upper surface of the piston when the reciprocating compressor is in a suction stroke (namely, when the piston is lowered to its maximum level. The distance between the TDC and BDC is called a stroke.
Based on the position of an initial state of the piston, as an amount of voltage (+ voltage) of one half period increases, the TDC is raised, and as an amount of voltage of the other half period increases, the BDC is lowered.
Herein, a time point at which the triac Tr1 is turned on to supply the voltage (+) voltage of one half period to control the TDC is called a TDC firing angle, and a time point at which the triac Tr1 is turned on to supply the voltage (− voltage of the other half period to control the BDC is called a BDC firing angle.
The related art apparatus and method for controlling an operation of the reciprocating compressor has a problem that the TDC and BDC cannot be independently controlled because the TDC firing angle and the BDC firing angle are controlling to be the same always.
In addition, because the TDC and BDC cannot be independently controlled, the size of the stroke of the reciprocating compressor cannot be maximized, failing to obtain maximum compression efficiency.